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Subject: Re: [RFC v1 07/11] net/mlx4: Cache irq_desc->affinity instead of irq_desc
From: Amir Vadai <amirv@mellanox.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Amir Vadai <amirv@mellanox.com>, Jiang Liu <jiang.liu@linux.intel.com>,
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On Mon, May 4, 2015 at 6:10 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Mon, 4 May 2015, Amir Vadai wrote:
>
>> On Mon, May 4, 2015 at 6:15 AM, Jiang Liu <jiang.liu@linux.intel.com> wrote:
>> > The field 'affinity' in irq_desc won't change once the irq_desc data
>> > structure is created. So cache irq_desc->affinity instead of irq_desc.
>> > This also helps to hide struct irq_desc from device drivers.
>>
>> Hi Jiang,
>>
>> I might not understand the new changes irq core, but up until now
>> affinity was changed when the user changed it through
>> /proc/irq/<IRQ>/smp_affinity.
>> This code is monitoring the affinity from the napi_poll context to
>> detect affinity changes, and prevent napi from keep running on the
>> wrong CPU.
>> Therefore, the affinity can't be cached at the beginning. Please
>> revert this caching.
>
> Sigh. All of this is completely wrong. Polling in the internals of
> irq_desc is just crap.
Hi,

>
> irq_set_affinity_notifier() has been added for exactly this purpose.
rmap is already registered on irq_set_affinity_notifier().
Actually, I did post an extension to the affinity notifier, to use
affinity chain which you rejected [1] (and BTW, convinced me that this
is not the way to do it).
Current code is according to your suggestion.

[1] - https://lkml.org/lkml/2014/5/26/222

Amir

>
> Please get rid of your irq_desc abuse.
>
> Thanks,
>
>         tglx
>
>
> --
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